A yacht captain has been found guilty of being drunk while erratically sailing a pleasure boat in a Dublin Port shipping lane.

Dublin Fire Brigade and RNLI lifeboats were called out to deal with an incident on the Liffey at Dublin Port at about 6am on 1 June 2017.

The sailors on a small 26-foot quarter tonne pleasure craft named the Peja refused to get out of the shipping lane and delayed the approach of the 90-metre Corinthian, a 4,000-tonne cruise liner, Dublin District Court heard.

The yacht skipper had insisted it was his "God-given right" to sail his vessel on the Liffey, while his co-accused stripped off when he made landfall on the city quays and was arrested naked.

It started after the small yacht left its mooring at a south Dublin bank sailing club.

After a couple of hours the sailing boat, which had an outboard engine, was brought to a halt at Sir John Rogerson's Quay while its owner was taken to Poolbeg Marina at about 8.20am.

Boat owner and yacht club member Brian Stacey, 46, of Derry Drive, Crumlin and co-defendant Ronan Stephens, 42, a former motorbike racer from Captain's Road also in Crumlin, faced charges under the Maritime Safety Act.

They denied careless sailing, operating a vessel while intoxicated and engaging in threatening and abusive behaviour, at the Shipping Lane on the River Liffey.

After a four-day non-jury trial, and a five-week adjournment to find a date to resume the case and to consider the verdict, Judge John Hughes found them guilty.

They will be sentenced next week.

Giving evidence, Stacey had told the court he and friends had gone for a sail early that morning.

There was no alcohol on board and he could not remember the last time he had an alcoholic drink, he claimed.

Questioned about CCTV showing him drinking from bottles, he denied garda evidence they contained beer and claimed they were foreign brand glass water bottles.

Stacey accused the rescue boats and a harbour-master pilot's boat of trapping his boat and he asked "what do you want?", but he added: "None of them would give me an answer."

He did not have a clue what was going on, he said.

The court heard he dropped off two passengers and went back onto the water. He later transferred to the pilot's vessel and instructed Mr Stephens to moor his boat.

He said that when he went onto the pilot's boat someone in a yellow jacket was yelling at him and trying to push him into the water.

Stacey claimed he was grabbed, but pushed the man away because he had no right. He explained to a garda on board that "I am a martial artist, if he has a go again, I will protect myself".

He agreed he was fuming but his was because the other boats were trying to destroy his pleasure craft.

He said he had been sailing for ten years and agreed best practice would have been to make radio contact with the harbour master earlier that morning. However, they did not answer the designated radio channel, he said.

Stacey denied claims he used profanities and told the court: "I told them it was my God-given right to sail down the Liffey if I feel like it."

He said he was not the sort of person that cursed.

"I don't believe what goes into my mouth defiles the body, it's what comes out the mouth that defiles the body, that is why I look after the hygiene in my mouth," he said.

"It was our God-given right to operate on the water," he said.

Asked why he was seen removing a number of bottles at one point when he moored, Stacey said he was cleaning out rubbish from his boat.

He said he was not breathalysed. His boat was going at walking pace and denied that it was sailed erratically.

His co-accused, a former motorcycle racer, said he had to dock the boat when his friend switched over to the harbour master's vessel.

Stephens said he had never operated a motor boat before and was obeying his co-accused's instruction because he was the captain.

The pleasure boat headed to Sir John Rogerson's Quay. CCTV evidence showed him being helped onto the quays where he removed all his clothing.

Mr Stephens said he did that because there were armed gardaí waiting and he was anxious and did not want to be shot.

He had to be helped because he suffered from arthritis and problems with his legs, he said. He also said Stacey was very Christian and did not use bad language.

He denied there was alcohol on the boat and also claimed there was just bottled water. He also said he did not drink during the day.

The pleasure boat was seized and destroyed, and the defence submitted it was missing evidence.